The present invention relates to an image processing apparatus and a method thereof, and more particularly, to an image processing apparatus which is designed to input image data and output it to a predetermined device and a method thereof.
In conventional image processing apparatus, such as a facsimile machine, an image is read by an image scanner, and each of the pixels of the raster scanned image is then expressed by binary data which is either white or black. For the telecommunication of the raster scanned binary image data, the raster scanned binary image is coded by the MH, MR or MMR method and then transmitted. Therefore, in the conventional facsimile machine, image data is internally handled by a set of raster scanned binary pixel data. When the resolution of the image read at the transmission side and the resolution of the reception side differ from each other, e.g., when the image read by the G3 machine (8 pel/mm in the horizontal direction and 7.7 line/mm in the vertical direction) is transmitted to a facsimile machine which has a standard recording resolution (8 pel/mm in the horizontal direction and 3.85 line/mm in the vertical direction), or when the paper size of the received image and that of the output image differ from each other, e.g., when the image received in B4 size is output to a sheet of recording paper having A4 size, the image data coded by the MH, MR or MMR method is converted into raster scanned binary image data, and then expansion (enlargement) or compression (reduction) is performed by simply double-writing each of the pixels (by writing the same pixel at least twice) or by thinning out the pixels.
However, in the above-described conventional image processing apparatus, when image data of a low resolution is recorded in the form of an image of a high resolution (which is internally the expansion/compression process of the image), e.g., when the image of 200 dpi is recorded on a sheet of recording paper of 400 dpi, the slanting contour line may be notched because of the simple doubling of each of the pixels. Furthermore, when a resolution conversion of about 200% is performed, e.g., when an image of the G3 resolution is converted into an image having the G4 resolution which is 200 dpi in both the horizontal and vertical directions, the image may be distorted because of the double thinning of each of the pixels.
Furthermore, in the conventional image processing apparatus, the quality of the original image data generated when an image original is read by a scanner may deteriorate due to the noises superimposed on the image signal generated by the scanner, that is, the image which is originally straight may be notched or black notches may appear on the white. In order to prevent such a deterioration in the image, attempts have been made to suppress the noise level of the image signal or to provide a mechanism of making the feed of the image original smooth. However, either of these methods has an deficiency.